The present invention relates to rotary to linear converters with lead screw. A rotary to linear converter according to the invention can be applied as head positioning mechanism of flexible magnetic disk drive.
The head positioning mechanism of disk drive comprises a stepping motor, a lead screw connected thereto, a head carriage to support a magnetic transducer head, a guide rod to move the head carriage along the radial direction of the magnetic disk, and an engagement member disposed between the lead screw and the head carriage.
U.S. Pat. No. 4,030,137 of Daiziel discloses an engagement member composed of a tubular portion which is threaded to mate with a lead screw. On the other hand, in order to simplify structure of the engagement member, another structure is also known where a ball or a pin is engaged with a helical groove of a lead screw.
In assembling work of a head positioning mechanism using a pin or a ball as engagement member, it is difficult to maintain constant distance between the lead screw and a guide rod of the carriage. If the distance varies, position of the pin in the axial direction of the lead screw also varies. As a result, position of the transducer head moving together with the pin varies on the disk and therefore the transducer head cannot be disposed to a desired position on the disk. Such problems may occur when a ball is used as engagement member.